Prosthesis sockets of this kind have long been known in the prior art and are used particularly with leg prostheses, for example in cases of above-knee amputation of the patient.
In known prosthesis sockets, the outer socket is, for example, made entirely of a fiber-reinforced plastic, for example a carbon-fiber-reinforced or glass-fiber-reinforced plastic. These materials are easy to work and are stable, and yet have a very low weight. In this way, it is possible to obtain a particularly light prosthesis or a particularly light prosthesis socket which nevertheless has good stability properties. In particular, the high degree of inherent stability of the outer socket gives the person wearing the prosthesis a feeling of security. The high degree of stability and strength of the outer socket also permits secure and stable attachment of distal prosthetic devices, for example a prosthetic foot, or a knee joint with an attached prosthetic lower leg and foot.
However, a disadvantage is that an amputation stump located in a prosthesis socket of this kind is largely or even completely shielded from perceptions of the environment. For example, when a person wearing a prosthesis fitted with a prosthesis socket of the type in question sits down and places his arms on his thighs, the rigid outer socket of the prosthesis socket does not allow him any possibility of corresponding feedback from his amputation stump. This therefore creates an unnatural and artificial sensation which greatly reduces the wearing comfort of a prosthesis fitted with such a prosthesis socket.
EP 0 760 640 B1 therefore discloses a prosthesis socket in which the outer socket is simply designed in the form of a receiving shell in which the distal end of the amputation stump is fitted. Starting from this receiving shell, three socket fingers extend to the proximal end of the prosthesis socket. These socket fingers are produced from a rigid and durable material and have a hook-and-loop fastening means on the inside face, i.e. the face directed toward the amputation stump. An inner socket, which is pulled on over the amputation stump itself, likewise has hook-and-loop fastening means at corresponding locations. The outer socket is secured on the inner socket through the cooperation of the hook-and-loop fastening elements on the inner socket and on the inside face of the outer socket. However, one disadvantage is that, by using hook-and-loop fastening means, relative movements can occur between the inner socket and the outer socket, particularly in the swing phase of a walking movement. Another disadvantage is that there is relatively little support particularly in the proximal region of the prosthesis socket, since the rigid outer socket does not extend into this region. The patient may therefore feel he has insufficient control over the prosthesis, which leads to increased instability and, consequently, to reduced wearing comfort.
U.S. Pat. No. 5,246,464 discloses a prosthesis socket with a rigid outer socket which is interrupted at some places. The outer socket nonetheless has an outer-socket edge which runs round the entire circumference of the amputation stump and defines the proximal end or proximal edge of the outer socket. As a result of the gaps provided in the rigid and fixed outer socket, an amputation stump located in the prosthesis socket is able to perceive the environment at least to a limited extent. In particular, objects lying on the amputation stump, or other parts of the patient's body supported on the amputation stump, for example the elbows, can be perceived inside these windows which are provided in the outer socket. However, since an outer socket of this kind has an outer-socket edge running all the way round the circumference, pressure sores and cuts can often occur here, which can lead to painful wounds.
The prior art therefore also discloses prosthesis sockets which have a rigid outer socket, but in which the outer-socket edge, which delimits the proximal opening of the outer socket, is formed at least partially by straps. Since these straps are responsible, at least in these regions of the outer socket edge, for the stability of the outer socket itself and for the secure arrangement of the prosthesis socket on the amputation stump, said straps have to be pulled relatively tight. This causes increased pressure on the amputation stump compared, for example, to an outer socket made entirely of a rigid material. This increased pressure on the amputation stump in the region of the straps can be very unpleasant for the wearer and may even become painful and lead to pressure sores and wounds.